1. Field of the Invention
This invention generally relates to a rolling contact bearing assembly, and, in particular, to a linear motion rolling contact bearing assembly of an enclosed type to thereby prevent dust and foreign matter from entering into the interior of the bearing assembly.
2. Description of the Prior Art
A linear motion rolling contact bearing assembly is well known in the art and it generally includes a bed or rail which extends straight over a desired length, a table or slider and a plurality of rolling members interposed between the bed and the table to thereby provide a rolling contact therebetween, so that the table may move linearly along the bed. In such a linear motion rolling contact bearing assembly, the bed includes a bottom wall and a pair of side walls which extend upright from the opposite sides of the bottom wall to thereby define a U-shaped cross section. And, a straight guide groove is provided at the inner surface of each of the pair of side walls. On the other hand, the table has a pair of outer side surfaces each of which is provided with a guide groove opposite to the corresponding guide groove of the bed. And, the plurality of rolling members, typically balls, are received in the paired guide grooves to thereby provide a rolling contact between the bed and the table. As a result, the table may move linearly relative to the bed.
In such a linear motion rolling contact bearing assembly, it is critical to keep the guide grooves and the rolling members clean and free of any foreign matter, such as dust. Otherwise, the rolling contact performance deteriorates and a high resistance may be created, which is detrimental to the performance of the linear motion rolling contact bearing assembly. In order to cope with this problem, the present inventor previously proposed to provide a dust-free structure to a linear motion rolling contact bearing assembly as disclosed in the U.S. Pat. No. 4,616,885, issued to the present inventor and assigned to the assignee of this application, which is hereby incorporated by reference. Although the structure disclosed in the above-mentioned patent provides a dust-proof environment, since the shielding member moves relative to the bed, the shielding member scrubs against the bed to thereby produce fine metal powder or dust, which then could be introduced into the guide grooves to thereby deteriorate the rolling performance. Thus, there has been a need to develop a further improvement in the structure of a dust-free rolling contact bearing assembly. Thus, as the table moves linearly relative to the bed, the shielding plate is unwound from or wound around the roller to thereby keep the interior space of the bearing assembly closed at all times.
With this structure, since there is no relative motion between the shielding means and the bed, the shielding means will not be scrubbed against the bed so that the production of metal powder or foreign matter, such as dust, is minimized, and, thus, the desired performance of the bearing assembly can be well maintained.
It is therefore a primary object of the present invention to obviate the disadvantages of the prior art as described above and to provide an improved dust-free linear motion rolling contact bearing assembly.
Another object of the present invention is to provide an improved dust-free linear motion rolling contact bearing assembly capable of preventing foreign matter, such as dust and metal powder, from being introduced into the rolling contact surfaces as much as possible.
A further object of the present invention is to provide an improved dust-free linear motion rolling contact bearing assembly compact in size, high in performance and stable in operation.